PV701 is the designation of a novel biologic therapeutic agent for cancer. It is a live, attenuated, triple-plaque purified strain of Newcastle disease virus (NDV), which is an avian paramyxovirus. The virus is grown in specific-pathogen-free chicken embryos and purified from the allantoic fluid. Preclinical tests indicate that PV701 preferentially replicates in and kills cancer cells without significantly affecting normal cells. Antitumor efficacy has been demonstrated against a wide variety of tumor cell lines, in vitro and in vivo. Thus, PV701 has the potential to be broadly active in malignant diseases, while producing relatively mild side effects. PV701 can be differentiated from other viruses which are currently in development for use against cancer in that it is not a human pathogen. As a consequence, pre-existing human immunity against this virus is not expected to be present. Therefore, PV701 can be administered with the expectation that tumors throughout the body will be exposed and eradicated by the virus. The primary objectives of this study are to establish the maximum tolerated dose (MTD) and identify the dose-limiting toxicity (DLT) of a single dose of of PV701. Frequency, severity, duration, and reversibility of adverse events will be tabulated and correlated with viral dose. In addition, the presence, magnitude, and duration of viral shedding, viremia and neutralizing antibodies will be determined. Secondary objectives are to evaluate the safety (cumulative toxicity) of repeated dosing, once the single dose MTD has been established. To establish the maximum tolerated dose (MTD) and identify the dose-limiting toxicity (DLT) of repeated dosing of PV701 following desensitization. To determine the safety of repeated intravenous dosing of PV701 over a two-week period and to document preliminary evidence of antitumor activity in cancer patients. Efficacy will be defined as a change in tumor response from baseline (complete response [CR] or partial response [PR], response duration, and time to tumor progression.